Center for Human Tissues and Organs Degeneration, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; National Innovation Center for Advanced Medical Devices, Shenzhen, China.
Center for Human Tissues and Organs Degeneration, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
Acta Biomater. 2021 May;126:524-536. doi: 10.1016/j.actbio.2021.02.045. Epub 2021 Mar 5.
Orthopedic and dental implants made of β-type Ti alloys have low elastic modulus which can better relieve the stress shielding effects after surgical implantation. Nevertheless, clinical application of β-type Ti alloys is hampered by the insufficient mechanical strength and gradual release of pro-inflammatory metallic ions under physiological conditions. In this study, the β-type Ti-45Nb alloy is subjected to high-pressure torsion (HPT) processing to refine the grain size. After HPT processing, the tensile strength increases from 370 MPa to 658 MPa due to grain boundary strengthening and at the same time, the favorable elastic modulus is maintained at a low level of 61-72 GPa because the single β-phase is preserved during grain refinement. More grain boundaries decrease the work function and facilitate the formation of thicker and less defective passive films leading to better corrosion resistance. In addition, more rapid repair of the passive layer mitigates release of metallic ions from the alloy and consequently, the inflammatory response is suppressed. The results reveal a strategy to simultaneously improve the mechanical and biological properties of metallic implant materials for orthopedics and dentistry. STATEMENT OF SIGNIFICANCE: The low modulus Ti-45Nb alloy is promising in addressing the complication of stress shielding induced by biomedical Ti-based materials with too-high elastic modulus. However, its insufficient strength hampers its clinical application, and traditional strengthening via heat treatments will compromise the low elastic modulus. In the current study, we enhanced the ultimate tensile strength of Ti-45Nb from 370 MPa to 658 MPa through grain-refinement strengthening, while the elastic modulus was maintained at a low value (61-72 GPa). Moreover, substrate grain-refinement has been proved to improve the corrosion resistance of Ti-45Nb with reduced inflammatory response both in vitro and in vivo. A relationship between the substrate microstructure and the surface passive layer has been established to explain the beneficial effects of substrate grain-refinement.
骨科和牙科植入物由β型钛合金制成，其弹性模量较低，可更好地缓解手术后植入物的应力屏蔽效应。然而，β型钛合金的临床应用受到机械强度不足和在生理条件下逐渐释放促炎金属离子的限制。在本研究中，β型 Ti-45Nb 合金经过高压扭转（HPT）处理以细化晶粒。经过 HPT 处理后，由于晶界强化，拉伸强度从 370MPa 增加到 658MPa，同时保持有利的弹性模量处于较低水平（61-72GPa），因为在细化晶粒过程中保留了单相β。更多的晶界降低了功函数，促进了更厚且缺陷较少的钝化膜的形成，从而提高了耐腐蚀性。此外，钝化层的更快修复减轻了合金中金属离子的释放，从而抑制了炎症反应。结果揭示了一种同时改善骨科和牙科金属植入材料机械和生物学性能的策略。
低模量 Ti-45Nb 合金有望解决因生物医学 Ti 基材料弹性模量过高而导致的应力屏蔽并发症。然而，其强度不足限制了其临床应用，而传统的热处理强化会损害其低弹性模量。在目前的研究中，我们通过晶粒细化强化将 Ti-45Nb 的极限拉伸强度从 370MPa 提高到 658MPa，同时保持弹性模量处于低值（61-72GPa）。此外，已证明基体晶粒细化可提高 Ti-45Nb 的耐腐蚀性，并减少体外和体内的炎症反应。已经建立了基体微观结构与表面钝化层之间的关系，以解释基体晶粒细化的有益效果。
